Updating expected action outcome in the medial frontal cortex involves an evaluation of error type

Abstract

Forming expectations about the outcome of an action is an important prerequisite for action control and reinforcement learning in the human brain. The medial frontal cortex (MFC) has been shown to play an important role in the representation of outcome expectations, particularly when an update of expected outcome becomes necessary because an error is detected. However, error detection alone is not always sufficient to compute expected outcome because errors can occur in various ways and different types of errors may be associated with different outcomes. In the present study, we therefore investigate whether updating expected outcome in the human MFC is based on an evaluation of error type. Our approach was to consider an electrophysiological correlate of MFC activity on errors, the error-related negativity (Ne/ERN), in a task in which two types of errors could occur. Because the two error types were associated with different amounts of monetary loss, updating expected outcomes on error trials required an evaluation of error type. Our data revealed a pattern of Ne/ERN amplitudes that closely mirrored the amount of monetary loss associated with each error type, suggesting that outcome expectations are updated based on an evaluation of error type. We propose that this is achieved by a proactive evaluation process that anticipates error types by continuously monitoring error sources or by dynamically representing possible response-outcome relations.

Figure 1.

Sequence of events on one trial of the flanker task. Participants had to classify the central target while ignoring the flankers. Because four response alternatives were used, two different types of errors could occur for incongruent stimuli. If participants responded by pressing the button associated with the flankers (button BK in the depicted example), an FE resulted. If participants responded by pressing a button not associated with an element in the stimulus array (buttons MV and WX in the depicted example), an NFE resulted.

Figure 2.

ERP data. A, B, Response-locked waveforms at electrode FCz for correct trials, FEs, and NFEs, separately for each group. C, D, Scalp topographies of the peak-to-peak Ne/ERN amplitudes, separately for each group. The mean latency of the Ne/ERN peak was 26 ms. R = time point of the button press.

Figure 3.

RT-matched ERP data. Response-locked waveforms at electrode FCz for correct trials, FEs, and NFEs for a subset of RT-matched trials, separately for each group. A, High NFE group. B, High FE group. R = time point of the button press.